| Refurbishment


WEIRS (OR LOW-HEAD DAMS) are described as being some of the “most abundant and impactful structures to freshwater ecosystems”, and over the past few decades there has been an increased effort to remove them, especially across Europe and North America. Existing weirs that exceed their lifespan have been


targeted for removal due to concerns over public safety and liability, as well as restoring water flows and the movement of sediments, materials, and species that have otherwise been impeded for up to 100 years or more.


Although many weirs have been completely


removed, there is a lack of understanding about the influential factors which determine whether planned removals go ahead or not. This has prompted a research team from the UK to investigate cases where planned removals have taken alternative trajectories, such as when a removal was intended but the weir remained, and a fish pass was constructed instead. As Januchowski-Hartley et al explain in their


research published in Conservation Science and Practice, they looked at how projects are carried out, any potential areas for improvement, and the sharing of lessons to facilitate the reconnection of more rivers. The study, described as being first of its kind in the UK, utilised mental models research which focuses on developing methods “to elicit and share people’s complex knowledge structures” and “reveal perceptions and assumptions that influence support for when, why, and how actions, such as weir removal, are done”. To do this the authors developed a group model that could be used to support learning and communication about weir remediation projects between individuals and groups. They added that the intention of the study was to explore, learn, and communicate, and not to quantify or predict different people’s perceptions of weir remediation.


Severn River The Severn River is the longest river in the UK, with


the Severn Estuary being designated a Special Area of Conservation. It was weir remediation in the Severn River Catchment (SRC) that was used as a case study for this work. The study focused on a six-year initiative called Unlocking the Severn under which six weir removals were proposed. Those involved in the SRC project worked with


the intention of completely removing weirs that were obstructing migratory fish species movement to historic spawning areas. However, complete removal was not achieved at any of the targeted weirs, and Januchowski-Hartley et al saw this an opportunity to work with people engaged in the remediation projects to determine how processes could be improved in the future. Semi-structured interviews were carried out with people who had been actively involved in the weir remediation processes across the Severn River Catchment. The results from the group mental model showed that weir remediation processes are influenced by a wider social–environmental context, such as drivers of fish decline, culture and heritage and governance, and by characteristics of the structure site (such as the weir’s form and size, and river hydrology) and of interested parties (such as weir ownership, and perceived benefits and costs).


After analysing their results, the authors found that implementation of catchment-scale planning would help to improve current approaches to weir remediation, while it was also argued that a coherent national strategy should shape where weirs are removed and where fish passes are built. Funding was perceived as a major point of failure in


the projects. Some respondents said that management of the environment in the UK “moves with what are the highest priorities at the time”, while “it is easier to raise money if you’ve got something tangible at the end”. The authors also suggested that there was a need for increased and directly allocated funding from government to support public engagement throughout project processes. Although current legislation in the UK dictates that fish passes must be built at any newly constructed weirs (including pre-existing structures with more than half the length destroyed or modified), this does not apply to existing weirs that are not otherwise partially (>50%) destroyed or modified. It was agreed that remediation projects would be more effective if existing legislation extended to weirs that are already in place and enforced the maintenance of the structure by owners in ways that promote river health and fish passage. A major point of failure in the SRC projects was locating and gaining permissions from land and weir owners, while improved engagement was also recommended. Improvements could focus on how people are consulted, such as hosting earlier consultations to better understand and consider people’s different perceptions and preferences in removal and/or fish pass scenarios. It was also suggested that improved partnerships between those working across the sectors involved in caring for rivers would benefit weir remediation project processes. This could include working directly between government agencies and river-charities, as well as with landowners and angling groups, to improve fish habitat. It was also suggested that contractors who design and build the weirs are involved when exploring different remediation options, working closely with landowners to anticipate problems associated with project implementation and to develop more acceptable outcomes. As full weir removal had been limited in the SRC, concern was expressed by several respondents about weir retention and building more infrastructure alongside them. The authors state that agreement was not reached in the group as to whether full weir


Below: Twaite shad being released in the River Severn. This fish species has been impacted by weir construction on the River Severn


www.waterpowermagazine.com | September 2024 | 23


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